I am from Iran...I want to travel Europe...It will be the second time, but I really can't find any people to provide me with an invitation. I want to know than is there any hotel or organisation that can help me...
The whole point of invitations as they are used in Western Europe (and in particular in the EU or Schengen area) is to make sure you have a genuine purpose and someone who is willing and able to host you. They are not necessary for tourism or any other purpose than visiting a person you already know and hotels do not extend any (nor do they need to).
That's the reason why hosts often have to provide a lot of information about their personal situation or their home for the invitation to be valid and useful. And people who issue fake invitations (e.g. to perform as “artist”) or help people who ultimately abscond or otherwise abuse their visa can expect trouble (or at least a loss of credibility).
This is quite unlike the mandatory invitations by a local agent and all the semi-official “fictional” invitations you can easily get in former soviet states. Unless you actually have some friends or family there, you can't expect to easily find someone willing to extend an invitation to Western Europe like you would in some other countries.
And even if you do, you have to understand that a transparently “fake” invitation can easily backfire and make you and your “host” guilty of fraud.